SQL Agent WMI Alert for file exist on remote server location

I have a SQL Agent Job that needs to be run only when there is a file existence on some remote server location that is shared like (\servername\foldername).

I Was trying to use WMI Alert in SQL Agent but not sure what to give in Namespace section of "New Alert" window for Type WMI event alert. And moreover WMI query that checks for the file existence.

Any help is greatly appreciated.

SQL Killer